A common problem experienced by owners of domestic fish aquariums is the necessity of periodically cleaning the tank and other aquarium components and its water supply to remove dissolved organic waste matter, particulate debris, chemical impurities such as ammonia and nitrate, and the like. The aquatic plants and animals living in an aquarium continuously shed or secrete particulate debris and dispense chemical impurities into the water supply, and it is necessary that the tank be routinely cleaned and that the water supply be routinely filtered to maintain a healthy environment in which the aquatic plants and animals may live.
Many domestic fish aquariums presently maintained in the United States include a perforated structure supported adjacent the bottom of the tank which is adapted to support a layer of gravel or similar rock material thereon, and aerating and water directing means for circulating air through the water to both supply oxygen to the aquatic plants and animals and to induce the water in the tank to circulate downwardly through the gravel bed and the perforated structure. The gravel bed acts to filter out physical impurities suspended in the water such as organic fish waste; and aerobic bacteria living in the gravel bed convert the organic waste into non-toxic gases which are then released into the water supply.
The conventional method of cleaning aquarium tanks generally requires that the aquatic plants and animals be removed from the tank along with the water, gravel, perforated structure and any other articles that may be within the tank. The gravel is then washed to remove particulate matter deposited thereon, and the tank is cleaned manually by scrubbing the interior walls to remove sedimentary deposits thereon. This task is time-consuming, laborious and very unpleasant; and the periodic cleaning of aquariums is generally the maintenance chore most commonly despised by owners of aquariums.
After the tank has been cleaned, the perforated structure, gravel and other articles are placed back in the tank, the tank is filled with fresh water and the fish and plants are returned to the tank. The fresh water used to refill the tank is not chemically equivalent to the water that has been removed, and provides an uncomfortable aquatic environment for the plants and animals. The fish are shocked when they are put back into the tank and remain agitated by the chemically unbalanced fresh water until they become accustomed to the water and the water approaches a proper chemical balance comfortable to the fish.
A conventional filter system such as described above is commonly referred to as an "undergravel filter" system. In such systems, the perforations in the support structure allow water and particulate matter to flow therethrough but prevent the gravel material from passing therethrough. The gravel bed acts as a filter as the aerobic bacteria living therein break down organic fish waste which has collected within the bed.
Systems for removing impurities from a fish aquarium water supply are known. One prior system, disclosed in U.S. Pat. No. 4,752,388, provides an undergravel fish tank filter comprising filter means; a rigid support for a gravel bed, and drive means for causing water from below the support to flow through the filter means. The water drawn from the base of the fish tank first passes downwardly through the gravel resting on the support to filter out part of the impurities from the water before the water is passed to the filter means. The drive means comprises a nozzle and an air tube. The nozzle extends upwardly from a chamber which is communicatively connected to the rigid support. Compressed air fed into the air tube issues in the form of bubbles which float upwardly from the tube, inducing a flow of water from below the structure to flow through the filter means, and out of the nozzle back into the main water body of the tank. The rigid support is also provided with apertures formed therein to ensure that large particulate material accumulating below the structure may be suctioned out from below the support.
A major shortcoming of such undergravel filter systems is that only a portion of the solid particulate matter in the water is trapped in the gravel bed to be broken down by the bacteria; a substantial portion of the matter passes through the perforations in the support structure and collects on the bottom surface of the tank. Furthermore, the draw created by the drive means is often insufficient to dislodge the particulate matter which deposits on the bottom surface of the tank, thereby failing to induce the matter to flow through the filtering device where it may be substantially removed from the water. The tank, therefore, must still be cleaned periodically by the conventional method to remove the particulate deposits on the bottom surface of the tank.
Other prior aquarium maintenance and filtration systems are exemplified by U.S. Pat. Nos. 3,759,223; 3,785,342; 4,098,230; 4,148,730; and 4,216,090. Efforts in the past to devise a system or method capable of effectively eliminating the need to periodically clean the aquarium tank by hand have not been successful to date.